Micro-structure formed of thin films

ABSTRACT

A substrate on which a plurality of thin films having a plurality of cross-sections corresponding to the cross-section of a micro-structure are formed is placed on a substrate holder. The substrate holder is elevated to bond a thin film formed on the substrate to the surface of a stage, and by lowering the substrate holder, the thin film is separated from the substrate and transferred to the stage side. The transfer process is repeated to laminate a plurality of thin films on the stage and to form the micro-structure. Accordingly, there are provided a micro-structure having high dimensional precision, especially high resolution in the lamination direction, which can be manufactured from a metal or an insulator such as ceramics and can be manufactured in the combined form of structural elements together, and a manufacturing method and an apparatus thereof.

This is a Continuation of application Ser. No. 09/791,634 filed Feb. 26,2001 which is a Division of application Ser. No. 09/064,056 filed Apr.22, 1998, now U.S. Pat. No. 6,245,249. The entire disclosure of theprior applications is hereby incorporated by reference herein in itsentirety.

BACKGROUND

1. Field of the Invention

This invention relates to micro-structures such as micro-gears,micro-optical parts, or molds for molding these micro-productsmanufactured by rapid prototyping, and a manufacturing method and anapparatus thereof, and more particularly relates to micro-structuresobtained by laminating thin films consisting of a metal or an insulatorwhich are patterned into sectional forms, and a manufacturing method andan apparatus thereof.

2. Description of Related Art

Rapid prototyping has been rapidly popularized recently as a method formolding three dimensional complex form products designed with the aid ofa computer within a short time. Three dimensional products manufacturedby rapid prototyping are used as parts models (prototype) of variousapparatus to predict the suitability of operation or form of parts. Thismethod has been mainly applied to relatively large parts having a sizeof several cm or larger, however, recently it has been desired to applythis method to manufacture micro-parts formed by precise working such asmicro-gears and micro-optical parts. Conventional methods formanufacturing such micro-parts described hereinafter have been known.

(1) Stereolithography (referred to as “conventional example 1”hereinafter)

(2) Selective laser sintering (referred to as “conventional example 2”hereinafter)

(3) Sheet lamination (referred to as “conventional example 3”hereinafter)

(4) Method using thin films as starting material (referred to as“conventional example 4” hereinafter)

CONVENTION EXAMPLE 1

FIG. 26 shows the conventional example 1 namely the stereolithography.In the “stereolithography”, photo-curable resin 100, which is hardenedby irradiation of light such as ultraviolet rays, is filled in a tank101, a laser beam 102 scans on the surface of the tank 101two-dimensionally to draw a form corresponding to the cross-sectionaldata of a three-dimensional product to harden the resin layer 100 a,then a stage 103 is lowered by one layer, and this process is repeatedlayer by layer to form the three dimensional product comprising aplurality of resin layers 100 a. Stereolithography is presented byIkuta, Nagoya University, in a literature “OPTRONICS, 1996, No. 4, p103”. According to the special stereolithography, planar form precisionof 5 μm and resolution in the lamination direction of 3 μm can beattained by optimization of exposure conditions and optimization ofresin characteristics. Stereolithography is also presented by Kawata,Osaka University, in a literature “Proceedings of MEMS 97, p 169”.According to this stereolithography, planar form precision of 0.62 μmand resolution in the lamination direction of 2.2 μm can be attained byutilizing a principle of two-photon absorption phenomenon.

CONVENTIONAL EXAMPLE 2

FIG. 27 shows the conventional example namely selective laser sintering.In the “selective laser sintering”, powder 104 is laid to form a thinlayer (powder layer) 104 a, a laser beam 102 is applied to the powderlayer 104 a to form a thin layer of a desired form, and by repeatingthis process a three dimensional sintered product composed of aplurality of powder layers 104 a is formed. According to the selectivelaser sintering, a three dimensional product not only of resin but alsoof ceramics and metals can be formed.

CONVENTIONAL EXAMPLE 3

FIG. 28 shows a manufacturing apparatus used in the conventional example3, namely the sheet lamination disclosed in Japanese PublishedUnexamined Patent Publication No. Hei 6-190929. In this manufacturingapparatus, when a plastic film 111 is supplied from a film feedingdevice 110, an adhesive coating device 120 coats photo-curable adhesive121 evenly on the underside of the plastic film 111 to form an adhesivelayer, a negative pattern exposure device 130 exposes an area of theadhesive layer excepting the area corresponding to the cross sectionalform of a micro-structure to form the hardened portion and the uncuredportion, this is pressed down by a press roller 141 of a photo-curinglaminating device 140, the uncured portion is hardened by the light froma light source 142 and bonded to the lower plastic film 111. The rearend of the plastic film 111 is cut by a laser beam from a CO₂ lasersource 151, and the border of the unnecessary area of the uppermostplastic film 111 is removed by the laser. This process is repeated layerby layer to form a micro-structure. In FIG. 28, 160 represents a workdevice for controlling this apparatus. According to the sheetlamination, a micro-structure comprising plastic sheets is obtained.

CONVENTIONAL EXAMPLE 4

FIG. 29 shows the conventional example 4, namely a manufacturing methodusing thin films as starting material disclosed in Japanese PublishedUnexamined Patent Publication No. Hei 8-127073. In this manufacturingmethod, as shown in the drawing (a), a photosensitive resin film 171 isformed on a substrate 170, and two processes, namely a process forforming an exposed portion 171 a by exposing on an area of a desiredpattern as shown in the drawing (b) and a process for forming anintermediate film 172 which prevents the resin film 171 from being mixedand prevents exposure of the lower layer, are repeated to form amulti-layer structure composed of the resin film 171 and intermediatefilm 172 as shown in the drawing (c), and then the exposed portion 171 ashown in the drawings (b) and (c) is selectively removed by dipping itin a resin developing solution and thus a three dimensionalmicro-structure as shown in drawing (d) is obtained. According to thismanufacturing method, the resolution in the lamination direction of Jimorder can be attained because spin coating is applied to the resin film171 and intermediate film 172.

However, according to the conventional example 1, namelystereolithography, this method is disadvantageous in that the resolutionin the lamination direction of 1 μm or smaller and the film thicknessprecision of 0.1 μm or smaller, which is required to manufacturemicro-gears and micro-optical parts, cannot be attained. In detail,because an incident light applied perpendicularly onto the layer forhardening the starting material (photosensitive resin) is used, theincident light penetrates perpendicularly from the surface through thelayer with decreasing intensity due to absorption, and the intensitydecreases to the level of the threshold value required for curing. Thelayer thickness corresponding to the threshold value is the thickness ofone layer, but because of dispersion of the incident light intensity,variation of the incident light intensity with time, and dispersion ofthe absorption coefficient of the starting material, it is difficult toobtain high resolution.

In addition, full cure process is applied to harden completely afterforming because photosensitive resin is used, in the full cure processthe product shrinks 1% through several %, the shrinkage isdisadvantageous and causes significant deterioration of the precision.

Furthermore, this method can be applied to only micro-structures made ofrelatively soft photosensitive resin, therefore, if a micro-structure isrequired to be made of a hard material such as a metal, the only way tomanufacture the product is the molding by electroforming or injectionmolding using a mold of this resin. The requirement of such process isdisadvantageous.

According to the conventional example 2, namely the selective lasersintering, the resolution in the lamination direction is poor because anincident light applied perpendicularly onto the layer is used as in theconventional example 1, and the shrinkage in full cure process causesdeterioration of precision, and furthermore the method isdisadvantageous in that a transfer process is required to manufacturemicro-structures made of a hard material such as metal.

According to the conventional example 3, namely the sheet lamination,the sheet thickness is the determinant factor of the resolution in thelamination direction, the lower limit is about several tens μm in viewof usable sheet thickness, and it is difficult to realize the resolutionin the lamination direction of 1 μm.

According to the conventional example 4, namely the manufacturing methodusing thin films as starting material, the intermediate film (forexample Al) is required in order to prevent exposure of the lower layerbecause an incident light applied approximately perpendicularly is usedin the exposure process, this method is disadvantageous in theresolution per one layer. Though a method in which two types ofphotosensitive resins of different sensitive wavelengths and differentsolubility in solvents are laminated alternately, the respectivephotosensitive resins are exposed, and finally developed to form a threedimensional product in order to omit the use of the intermediate film,is disclosed in the patent, because this method is still disadvantageousin that the adhesion between resins of different solubility in solventsis poor, the strength of a completed product is low, and the dimensionalprecision is poor due to swelling of the photosensitive resin in thefinal development process. Furthermore, it is impossible to apply thismethod directly to hard material such as metals and insulators as in theabove-mentioned stereolithography because photosensitive resin is used,and the only way is a method in which a product is used as a mold.

Accordingly, it is an object of the present invention to providemicro-structures of high dimensional precision and, particularly, highresolution in the lamination direction and a manufacturing method and anapparatus thereof.

It is another object of the present invention to providemicro-structures which are formed directly of metals or insulators suchas ceramics and a manufacturing method thereof and an apparatustherefor.

It is yet another object of the present invention to providemicro-structures which can be formed together from a plurality ofcombined structural elements and a manufacturing method and an apparatusthereof.

SUMMARY OF THE INVENTION

To achieve the above-mentioned object, the present invention provides amicro-structure comprising a plurality of laminated thin films havingprescribed two-dimensionally patterned forms.

To achieve the above-mentioned object, the present invention provides amanufacturing method of micro-structures composed of a first step forforming a plurality of thin films having prescribed two-dimensionallypatterned forms on a substrate, and a second step for forming themicro-structure by separating the plurality of thin films from thesubstrate and subsequently by laminating and bonding the plurality ofthin films on a stage.

To achieve the above-mentioned object, the present invention provides amanufacturing method of micro-structures including;

a first step for forming a plurality of first thin films having aprescribed two-dimensional pattern on a substrate, and forming aplurality of second thin films composed of different material from thatof the first thin films and having the same film thickness as the firstthin film to form a plurality of composite thin films comprising thefirst thin films and the second thin films,

a second step for forming a laminate including a micro-structure bylaminating and bonding the plurality of composite thin films on a stage,and

a third step for removing the first thin films or the second thin filmsout of the substrate to obtain the micro-structure.

To achieve the above-mentioned object, the present invention provides amanufacturing method of micro-structures including;

a first step for forming a thin film respectively on a plurality ofsubstrates and forming a plurality of latent images having a prescribedtwo-dimensional pattern on each thin film formed on the plurality ofsubstrates,

a second step for bonding the thin films each other on which the latentimages are formed,

a third step for removing one substrate out of a pair of substrateshaving the thin films bonded each other,

a fourth step for laminating a plurality of thin films by repeating thesecond step and the third step, and

a fifth step for developing the latent images out of the plurality oflaminated thin films.

To achieve the above-mentioned object, the present invention provides amanufacturing apparatus of micro-structures provided with;

a substrate holder having a substrate on which a plurality of thin filmsare formed thereon having a prescribed two-dimensional pattern providedin a vacuum chamber,

a stage disposed facing the substrate holder in the vacuum chamber forsupporting a three-dimensional structure formed by laminating theplurality of thin films,

a moving means for transferring at least either of the substrate holderand the stage to position the stage successively on the plurality ofthin films, and

a control means for controlling the moving means to separate theplurality of thin films from the substrate, to laminate and bond theplurality of thin films on the stage so as to form a micro-structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram for illustrating a manufacturing system inaccordance with the first embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a lamination equipment inaccordance with the first embodiment.

FIG. 3 is a block diagram for illustrating a control system of thelamination device in accordance with the first embodiment.

FIG. 4 is a diagram for describing the relation between the bondingstrength of a sacrificial layer, a thin film, and a releasing layer inthe first embodiment.

FIG. 5 is a perspective view of a target micro-structure of the firstembodiment.

FIG. 6 is a set of diagrams, FIG. 6(a) shows a thin film depositionprocess in accordance with the first embodiment, and FIG. 6(b) and FIG.6(c) show the patterning process in accordance with the firstembodiment.

FIG. 7 is a set of diagrams, FIGS. (a) through (c) show the laminationprocess in accordance with the first embodiment.

FIG. 8 is a set of diagrams, FIGS. (a) through (c) show the laminationprocess in accordance with the first embodiment.

FIG. 9 is a cross-sectional view for showing completion of a laminationprocess in accordance with the first embodiment.

FIG. 10 is a set of diagrams, FIG. 10(a) is an exploded perspective viewof a micro-pulley, namely a micro-structure, and FIG. 10(b) is across-sectional view of the micro-pulley.

FIG. 11 is a set of diagrams, FIGS. 11(a) through (e) show the filmdeposition and patterning process in accordance with the secondembodiment.

FIG. 12 is a plan view of a substrate for showing the patterning processin accordance with the second embodiment.

FIG. 13 is a plan view of a substrate for showing the patterning processin accordance with the second embodiment.

FIG. 14 is a cross-sectional view for showing laminated cross-sectionalelements of the first layer through twentieth layer in accordance withthe second embodiment.

FIG. 15 is a set of diagrams, FIG. 15(a) is an exploded perspective viewof a target micro-gear of the second embodiment, and FIG. 15(b) is alongitudinal cross-sectional view of the micro-gear.

FIG. 16 is a plan view for showing a thin film deposition substrate inaccordance with the third embodiment of the present invention.

FIG. 17 is a set of diagrams, FIGS. 17(a) through (d) are plan views forshowing a thin film deposition substrate in accordance with the thirdembodiment of the present invention.

FIG. 18 is a cross-sectional view for showing laminated chips of thefirst layer through twentieth layer in accordance with the thirdembodiment.

FIG. 19 is a schematic structural diagram of the patterning equipment inaccordance with the fourth embodiment of the present invention.

FIG. 20 is a perspective view of a target micro-structure of the fourthembodiment.

FIG. 21 is a plan view of a substrate for showing the patterning processin accordance with the fourth embodiment.

FIG. 22 is a cross-sectional view for showing laminated cross-sectionalelements of the first layer through n-th layer in accordance with thefourth embodiment.

FIG. 23 is a block diagram for illustrating a manufacturing system inaccordance with the fifth embodiment of the present invention.

FIG. 24 is a set of diagrams, FIGS. 24(a) through (d) are diagrams forshowing a manufacturing method in accordance with the fifth embodiment.

FIG. 25 is a set of diagrams, FIGS. 15(a) through (d) are diagrams forshowing a manufacturing method in accordance with the fifth embodiment.

FIG. 26 is a schematic diagram for illustrating the stereolithography ofthe conventional example 1.

FIG. 27 is a schematic diagram for illustrating the selective lasersintering of the conventional example 2.

FIG. 28 is a diagram for illustrating a manufacturing apparatus inaccordance with the sheet lamination of the conventional example 3.

FIG. 29 is a set of diagrams, FIGS. 29(a) through (d) show amanufacturing method of the conventional example 4 in which thin filmsare used as starting material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a manufacturing system of micro-structures in accordancewith the first embodiment of the present invention. The structure ofthis manufacturing system 1 comprises a film deposition equipment 2A fordepositing a thin film on a substrate, a patterning equipment 2B forpatterning a pattern on the thin film formed by the film depositionequipment 2A corresponding to cross-sectional forms of an objectmicro-structure, and a lamination equipment 3 for laminating a pluralityof patterned thin films by surface activated bonding.

The film deposition equipment 2A controls excellently the film thicknessof a film deposited on a substrate such as an Si wafer, a quartzsubstrate, or a glass substrate (for example, Corning 7059) in athickness range from sub μm through several μm, and forms a thin filmby, for example, vacuum vapor deposition such as electron beamdeposition, resistance heating vapor deposition, sputtering, or chemicalvapor deposition (CVD), or spin coating which gives a film with eventhickness through the entire substrate. By applying vacuum vapordeposition or spin coating, a film with a thickness of 0.1 through 10 μmis deposited with a film thickness precision of 1/10 the film thicknessor smaller.

The film deposition equipment 2A previously forms a releasable releasinglayer on the surface of a substrate prior to deposition or coating of athin film. The releasing layer may be a thin film of thermal oxide orfluorine-containing resin formed by vapor deposition or coating on thesurface of a substrate, or may be formed by a method that the substratesurface is exposed to discharge in a gas containing fluorine tofluoridize the substrate surface. The releasability is enhanced byforming a thin film containing fluorine or fluoridation.

The patterning equipment 2B forms a plurality of thin films having formsrespectively corresponding to each cross-sectional form of amicro-structure by removing unnecessary portions or circumferencetogether using a patterning method for patterning with a planerprecision within 0.1 μm, for example, photolithography, focused ion beammethod (FIB), or electron beam lithography. By applying lithography, theplanar precision of sub μm is obtained, and the productivity isenhanced. By applying FIB method and electron beam lithography, theplanar precision of sub μm is obtained, and a film is patterned withoutusing a photo-mask because an arbitrary form is drawn by beam scanning,hence the time for manufacturing of photomasks is saved. In the case ofthe electron beam lithography, electron beam resist which is sensitiveto an electron beam is used as the resist. In the first embodiment,unnecessary portions are removed by photolithography.

FIG. 2 shows a schematic structure of the lamination equipment 3. Thelamination equipment 3 is provided with a vacuum chamber 300 in which alamination process is performed, and in the vacuum chamber 300, asubstrate holder 301 on which a substrate 400 is placed and fired, astage 302 to which a thin film formed on the substrate 400 istransferred, the first FAB source 303A for FAB (Fast Atom Bombardment)of the stage 302 side and the second FAB source 303B for FAB of thesubstrate 400 side both attached to the stage 302, the first and secondwithdrawing motors 305A and 305B for withdrawing the first and secondFAB sources 303A and 303B by rotating arms 304A and 304B about 90° afterFAB, a mark detection unit 306 for detecting an alignment mark on thesubstrate 400 as a microscope mounted on the stage 302, a vacuum gauge307 for measuring the degree of vacuum in the vacuum chamber 300, anX-axis table 310 for moving the stage 302 in the X-axis direction(horizontal direction in FIG. 2) using an X-axis motor 311 (refer toFIG. 3) and for detecting the position of the stage 302 on the X-axisusing an X-axis position detection unit 312 (refer to FIG. 3), and aY-axis table 320 for moving the stage 302 in the Y-axis direction (inthe direction perpendicular to the page plane) using a Y-axis motor 321(refer to FIG. 3) and for detecting the position of the stage 302 on theY-axis are provided. Herein, “FAB” means a treatment that, for example,argon gas which is accelerated by a high voltage of about 1 kV isapplied onto the surface of a material as an atom beam to remove oxidefilm and impurities on the material surface and to clean the surface. Inthis embodiment, the FAB irradiation conditions are varied depending onmaterial to be treated, in detail, the acceleration voltage is varied ina range from 1 through 1.5 kV, and irradiation time is varied in a rangefrom 1 to 10 minutes.

The stage 302 consists of a metal such as stainless steel or aluminum,and a sacrificial layer is formed previously on the surface in order toseparate the microstructure easily from the stage 302 themicro-structure comprising a plurality of thin films laminated on thestage 302. Material used for the sacrificial layer is selected dependingon the material of the micro-structure. In detail, for themicro-structure made of a metal such as aluminum, copper or nickel isselected as the material of the sacrificial layer, and in this case, acopper or nickel layer with a thickness of, for example, about 5 μm isformed on the surface of the stage 302 by plating. For themicro-structure which comprises thin films of an insulator, namelyceramics such as alumina, aluminum nitride, silicon carbide, or siliconnitride, aluminum is selected as the material of the sacrificial layer,and in this case, an aluminum layer is formed on the surface of thestage 302 by vacuum vapor deposition. By removing only the sacrificiallayer after completion of thin film lamination, the micro-structure isseparated easily from the stage 302 without an external force applied tothe micro-structure.

The lamination equipment 3 is provided with a Z-axis table 330, a θtable 340, a vacuum pump 350, an argon gas cylinder 351, and the firstand second flow rate controllers (MFC) 353A and 353B. The Z-axis table330 is served for moving the substrate holder 301 in the Z-axisdirection (vertical direction in FIG. 2) to the outside of the vacuumchamber 300 using a Z-axis motor 331 (refer to FIG. 3), for pressing thethin film onto the stage 302 side with a pressure of 5 kgf/cm² or higherfor 1 through 10 minutes, and for detecting the position of thesubstrate holder 301 on the Z-axis using a Z-axis position detectionunit 332 (refer to FIG. 3) The θ table 340 is served for rotating thesubstrate holder 301 round the Z-axis using a θ motor 341 for alignmentadjusting, and for detecting the angular position in the θ-direction ofthe substrate holder 301 using a θ position detection unit 342 (refer toFIG. 3). The vacuum pump 350 is served for evacuating the internal ofthe vacuum chamber 300 to a vacuum. The argon gas cylinder 351 containsargon gas. The first and second mass flow controllers (MFC) 353A and353B are served for controlling the flow rate of argon gas supplied fromthe argon gas cylinder 351, and for supplying argon gas to the first andsecond FAB sources 303A and 303B through the first and second solenoidvalves 352A and 352B.

FIG. 3 shows a control system of the lamination equipment 3. Thelamination equipment 3 has a control unit 360 for controlling thisequipment 3 wholly, and the control unit 360 is connected to variousunits namely a memory 361 for storing various information includingprograms of the control unit 360, the first FAB source 303A via thefirst FAB source driving unit 362A, the second FAB source 303B via thesecond FAB source driving unit 362B, the first and second withdrawingmotors 305A and 305B, the mark detection unit 306, the vacuum gauge 307,the X-axis motor 311, the X-axis position detection unit 312, the Y-axismotor 321, the Y-axis position detection unit 322, the Z-axis motor 331,the Z-axis position detection unit 332, the θ motor 341, the θ positiondetection unit 342, the vacuum pump 350, the first and second solenoidvalves 352A and 352B, and first and second MFCs 353A and 353B.

For example, a laser interferometer or glass scale may be used as theX-axis position detection unit 312, the Y-axis position detection unit322, and the θ position detection unit 342.

The first and second FAB source driving units 362A and 362B supply anacceleration voltage of 1 though 1.5 kV to the corresponding first andsecond FAB sources 303A and 303B.

The control unit 360 controls respective units in the laminationequipment 3 to perform the process in which the thin film formed on thesubstrate 400 with interposition of the releasing layer is bonded on thesurface of the stage 302 with interposition of the sacrificial layer, aplurality of thin films separated from the substrate are bonded andlaminated successively on the thin film to form a micro-structure basedon programs stored in the memory 361.

FIG. 4 shows a diagram for describing the bonding strength between thesacrificial layer, thin film, and releasing layer. Assuming that thebonding strength between the releasing layer 401 and the thin layer 4 ais represented by f₁, the bonding strength between thin films 4 a and 4a is represented by f₂, and the bonding strength between the thin film 4a and the sacrificial layer 370 is represented by f₃, then the materialof the sacrificial layer 370, releasing layer 401, and thin film 4 a isselected so that the order of the strength is in the relation off₂>f₃>f₁. As the result, the thin film 4 a formed on the substrate 400with interposition of the releasing layer 401 is bonded to thesacrificial layer 370 on the stage 302 or bonded to the thin film 4 atransferred already on the stage 302 with sufficient strength, and canbe separated from the substrate 400 and transferred to the stage 302side.

Next, operations of the manufacturing system 1 in accordance with thefirst embodiment are described with reference to FIG. 5 and FIG. 6.Herein it is assumed that the sacrificial layer 370 is formed previouslyon the stage 302.

FIG. 5 shows one example of a micro-structure to be manufactured in thefirst embodiment. The micro-structure 4 comprises a plurality of thinfilms 4 a respectively corresponding to each cross-sectional form.

FIGS. 6(a) through (c) show a film deposition process and patterningprocess.

(1) Film Deposition

As shown in FIG. 6(a), by using the film deposition equipment 2A, athermal oxide film with a thickness of 0.1 μm is grown on the surface ofa substrate 400, namely an Si wafer, as the releasing layer 401, and anAl thin film 402 with a thickness of 0.5 82 μm is formed on the thermaloxidized film by sputtering. High purity Al is used for a sputteringtarget, the sputtering pressure is 0.5 Pa and the temperature of thesubstrate is a room temperature. The film thickness is monitoredcontinuously by a quartz oscillator film thickness meter during filmdeposition, the film deposition process terminates when the filmthickness reaches 0.5 μm. As the result, the film thickness on thesubstrate 400 with distribution within 0.5±0.02 μm is obtained. The filmthickness is the determinant of the resolution in the laminationdirection of the micro-structure obtained finally, and sufficientattention should therefore be paid to the film thickness and filmthickness distribution.

(2) Patterning

As shown in FIGS. 6(b) and 6(c), a plurality of thin films 4 arespectively corresponding to each cross-sectional form of themicro-structure 4 shown in FIG. 5 is formed by photolithography. Indetail, positive type photo-resist is coated on the surface of the Althin film 402 formed on the substrate 400, the photo-resist is exposedto light with covering by a photo-mask (omitted from the drawing), theexposed portion of the photo-resist is removed by a solvent, the exposedportion of the thin film 402 is etched, and the unexposed photo-resistis removed by a resist remover leaving the plurality of thin films 4 aon the substrate. When a plurality (for example three) of alignmentmarks 403 for positioning, the substrate 400 in a patterning process isalso formed. In FIGS. 6(b) and 6(c), the respective thin films 4 a aredesignated as the first layer through the sixth layer in order ofdiameter from the largest one through smallest one for the purpose ofdescription.

FIGS. 7(a) through 7(c) and FIGS. 8(a) through 8(c) show the laminationprocess described hereinafter. In FIG. 8, the releasing layer 401 andsacrificial layer 370 are omitted from the drawings.

(3) Introduction of the Substrate 400 into the Vacuum Chamber 300

The substrate 400 on which the plurality of thin films 4 a are formed isplaced and fired on the substrate holder 301 in the vacuum chamber 300of the lamination equipment 3.

(4) Evacuation of the Inside of the Vacuum Chamber 300

When an operator pushes down a starting switch (not shown in thedrawing) of the lamination equipment 3, the control unit 360 performsthe process described hereinafter according to the program stored in thememory 361. First, the control unit 360 controls the vacuum pump 350based on the vacuum value detected by the vacuum gauge 307 to evacuatethe inside of the vacuum chamber 300 to 10⁻⁶ Pa, and the inside of thevacuum chamber 300 is brought to the condition of high vacuum orultra-high vacuum.

(5) Alignment Adjustment

After the evacuation, the control unit 360 performs alignment adjustmentof the stage 302 and the substrate 400 (alignment mark 403). In detail,the control unit 360 controls the X-axis motor 311 and the Y-axis motor321 so as to obtain a mark detection signal from the mark detection unit306 by moving the stage 302 in the X-direction and Y-direction, measuresthe relative positional relation between the substrate 400 and substrateholder 301 based on the mark detection signal, and controls the X-axismotor 311, the Y-axis motor 321, and the motor θ 341 so that the stage302 and alignment mark 403 reach the original position based on themeasurement result of the relative position relation. The stage 302 ismoved in the X-direction and the Y-direction respectively by the X-axismotor 311 and the Y-axis motor 321, the substrate holder 301 is rotatedby the θ motor 341, and the stage 302 and alignment mark 403 reach theoriginal position. Hence, even though the position where the substrate400 on which the thin films 4 a are formed is placed deviates from thecorrect position, the relative position between the stage 302 and thealignment mark 403 is set correctly.

(6) Removal of the Contaminated Layer on the Surface to be Bonded to theFirst Layer Thin Film 4 a

As shown in FIG. 7(a), the control unit 360 drives the X-axis motor 311and the Y-axis motor 321 based on the detection signal of the X-axisposition detection unit 312 and the Y-axis position detection unit 322,and moves the stage 302 from the original position in the X-directionand Y-direction to position the stage 302 on the first layer thin film 4a. Then the control unit 360 irradiates an argon atomic beam 351 a ontothe surface (the surface of the stage 302 and the surface of the firstlayer thin film 4 a) where the first layer thin film 4 a is to be bondedfor FAB treatment. In detail, the control unit 360 performs drivingcontrol on the first and second FAB source driving units 362A and 362B,operation control on the first and second solenoid valves 352A and 352B,and flow rate control on the first and second MFCs 353A and 353B so thatthe argon atomic beam 351 a is applied onto the surface of the stage 302and the surface of the first layer thin film 4 a with a prescribed ratefor a prescribed time (for example, 5 minutes). The first and second FABsource driving units 362A and 362B are controlled by the control unit360 so as to provide an acceleration voltage of, for example, 1.5 kV tothe first and second FAB sources 303A and 303B. The flow rate of argongas supplied from the argon gas cylinder 351 is controlled by the firstand second MFCs 353A and 353B, and argon gas is supplied to the firstand second FAB sources 303A and 303B through the first and secondsolenoid valves 352A and 352B. The first FAB source 303A irradiates theargon atomic beam 351 a for 5 minutes onto the surface of the stage 302which is located off the upper direction at an angle of about 45°. Thesecond FAB source 303B irradiates the argon atomic beam 351 a for 5minutes onto the surface or the first layer thin film 4 a which islocated off the lower direction at an angle of about 45°. Thecontaminated layers with a thickness of less than 10 nm on the surfaceof the stage 302 and the first thin film 4 a are removed thereby. Suchsmall thickness decrement can be neglected because the number ofdecrement is one figure smaller than the target film thickness precisionof 0.1 μm of the present invention.

(7) Bonding of the First Layer Thin Film 4 a

Next, as shown in FIG. 7(b), the control unit 360 drives the first andsecond withdrawing motors 305A and 305B to rotate the arms 304A and 304Bin the horizontal direction, and withdraws the first and second FABsources 303A and 303B. The control unit 360 controls the Z-axis motor331 based on the detection signal of the Z-axis position detection unit332 to elevate the substrate holder 301, the surface of the first layerthin film 4 a is forced to be in contact with the surface of the stage302, and the contact continues for a prescribed time (for example, 5minutes) with a prescribed pressure (for example, 50 kgf/cm²). Thesurface of the first layer thin film 4 a is bonded to the surface of thestage 302 (sacrificial layer 370) strongly. A tensile test forevaluation of the bonding strength between the thin film 402 and thesacrificial layer 370 shows 50 through 100 Mpa. Preferable surfaceroughness of the thin film 4 a and stage 302 is respectively about 10 nmfor obtaining excellent bonding strength.

(8) Transfer of First Layer Thin Film 4 a

Next, as shown in FIG. 7(c), the control unit 360 drives the Z-axismotor 331 based on the detection signal of the Z-axis position detectionunit 332 to lower the substrate holder 301 to the original positionshown in FIG. 7(a), and drives the first and second withdrawing motors305A and 305B to return the first and second FAB sources 303A and 303Bto the original position. By lowering the substrate holder 301, the thinfilm 4 a is separated from the substrate 400 and transferred to thestage 302 side because the bonding strength f₃ between the thin film 4 aand the sacrificial layer on the stage 302 is larger than the bondingstrength f₁ between the thin film 4 a and the releasing layer.

(9) Removal of a Contaminated Layer on the Surface to be Bonded to theSecond Layer Thin Film 4 a

Next, as shown in FIG. 8(a), the control unit 360 controls the X-axismotor 311 and the Y-axis motor 321 to move the stage 302 above thesecond layer thin film 4 a, and irradiates again FAB as described inFIG. 7(a). The moving distance of the stage 302 is a distancecorresponding to each thin film 4 a pitch. This FAB irradiation isdifferent from the first FAB irradiation in that the back surface of thefirst layer thin film 4 a (the surface which has been in contact withthe substrate 400) is irradiated for cleaning instead of the surface ofthe stage 302.

(10) Bonding of the Second Layer Thin Film 4 a

Next, as shown in FIG. 8(b), the control unit 360 withdraws the firstand second FAB sources 303A and 303B, elevates the substrate holder 301to bond the second layer thin film 4 a to the first layer thin film 4 a.

(11) Transfer of the Second Layer Thin Film 4 a

Next, as shown in FIG. 8(c), the control unit 360 lowers the substrateholder 301, returns the first and second FAB sources 303A and 303B tothe original position, and lowers the substrate holder 301. By loweringthe substrate holder 301, the second layer thin film 4 a is separatedfrom the substrate 400 side and transferred onto the first thin film 4 abecause the bonding strength f₂ between thin films is larger than thebonding strength f₁ between the thin film 4 a and the releasing layer401.

(12) Removal of the Sacrificial Layer 370

FIG. 9 shows the state that all the thin films 4 a have been laminated.By repeating bonding and transferring of thin films 4 a of the thirdlayer through sixth layer successively, a micro-structure 4 comprisingall the laminated thin films 4 a is obtained. Finally the sacrificiallayer 370 is removed by etching and the micro-structure 4 is separatedfrom the stage 302.

The effect of the above-mentioned first embodiment is describedhereinafter,

(a) A plurality of thin films 4 a which are components of amicro-structure are formed simultaneously together by film depositionand patterning, the plurality of thin films 4 a are laminated thereforesimply by repeating bonding and transfer processes, thus theproductivity is enhanced significantly. Micro-structures aremanufactured efficiently because once the vacuum chamber 300 isevacuated, a set of irradiation of FAB, bonding, and transfer processescan be performed continuously without breaking the vacuum.

(b) A plurality of thin films corresponding to each cross-sectional formof a micro-structure is formed together by one process of filmdeposition and patterning, it is therefore possible to save the timerequired for the whole process significantly.

(c) By injection molding of plastics using the obtained micro-structure4 as a mold, micro-optical parts such as optical lenses aremass-produced.

(d) Because the thin film 4 a is bonded to the stage 302 side by surfaceactivated bonding, it is not necessary to use an adhesive or to dissolvethe material, and therefore the form and thickness of the thin film 4 awill not change when bonding, thus high precision is maintained.

In this embodiment, thin films are bonded by surface activated bonding,however, the thin films may be bonded by bonding with an adhesive, ordiffusion bonding with heating.

In this embodiment, the thin films are patterned after film deposition,however, alternatively, a simultaneous film deposition and patterning,for example, a method using a metal mask, or selective CVD may be used.

In this embodiment the Al thin film is formed by sputtering, howeveralternatively, the Al thin film may be formed by resistance heatingvapor deposition or electron beam heating vapor deposition.

Further, the material used for the thin film is not limited to Al, butalternatively other metals such as tantalum (Ta), copper, or indium maybe used, and ceramics such as alumina, aluminum nitride, siliconcarbide, or silicon nitride may also be used.

In this embodiment the case that the substrate holder 301 is moved inthe Z-direction, and the stage 302 is moved in the X-direction and theY-direction is described, however, a case that both the substrate holder301 and the stage 302 are moved in the Z-direction, a case that thesubstrate holder 301 is moved in the X-direction and the Y-direction,and the state 302 is moved in the Z-direction, or a case that thesubstrate holder 301 and the stage 302 have the same structure may beused.

A set of processes of film deposition, patterning, bonding, andtransferring may be repeated on every thin film 4 a.

Next, a manufacturing system in accordance with the present inventionwill be described hereinafter. The manufacturing system is provided witha film deposition equipment, a patterning equipment, and a laminationequipment like the first embodiment, but different in that the filmdeposition equipment and patterning device are structured so as to forma plurality of first thin films corresponding to each cross sectionalform of a micro-structure by a lift off method, and different in that apolishing device not shown in the drawing for polishing the surface of asubstrate by CMP (Chemical Mechanical Polishing) is provided in order toform the second thin film made of the different material from that ofthe first thin film and having the same thickness as that of the firstthin film around the first thin film.

Next, operations of the manufacturing system in accordance with thesecond embodiment are described with reference to FIG. 10 and FIG. 11hereinafter.

FIG. 10 shows a micro-pulley namely micro-structure 4 to be manufacturedin the second embodiment, FIG. 10(a) is an exploded perspective view andFIG. 10(b) is a longitudinal cross-sectional view. The micro-structure 4shown in the drawing is composed of the first layer through twentiethalumina thin films 4 a, and has a structure that a shaft 41 providedwith flanges 40 and 40 on both ends thereof is inserted into an opening43 a of the pulley 43 provided with collars 42 and 42.

FIG. 11 shows film deposition and patterning processes.

As shown in FIG. 11(a), by using the film deposition equipment, athermal oxide film with a thickness of 0.1 μm is grown on the surface ofthe substrate 400, namely an Si wafer, as the releasing layer 401. Then,photo-resist 404 is coated on the releasing layer 401 over the entiresurface, portion of the photo-resist corresponding to eachcross-sectional form of the micro-structure 4 is separated by patterningof exposure and development, and the first thin film 402A with athickness of 1 μm made of alumina (Al₂O₃) is deposited over the entiresurface using the film deposition equipment.

Next, as shown in FIG. 11(b), the residual photo-resist 404 is removedtogether with the first thin film 402A formed thereon (lift off method).The residual first thin film 402A is the thin film 4 a to be thecomponent of the micro-structure 4.

Then, as shown in FIG. 11(c), the second thin film 402B consisting ofaluminum (Al) with a thickness of 1.1 μm is formed by sputtering usingthe film deposition equipment. At this stage, the first thin film 402Ais covered over the entire surface with the second thin film 402B. Inthis embodiment, the combination of the first thin film 402A of Al₂O₃and the second thin film 402B of Al is selected because these materialsare bonded easily to each other by surface activated bonding andselectively removable.

Next, as shown in FIG. 11(d), the surface of the second film 402B ispolished to remove the second thin film 402B by the CMP method using thepolishing equipment until the first thin film 402A (4 a) is exposed. Thethickness of both the Al₂O₃ thin film and Al thin film 402B becomes 1μm. The surface roughness of the Al₂O₃thin film 4 a is about 10 nm likethe stage 302. The roughness helps obtain a high bonding strength f₂between the thin films 4 a and 402B.

FIG. 12 is a plan view corresponding to FIG. 11(d). During patternforming shown in FIG. 12, a plurality (for example, three) of alignmentmarks 403 are formed.

Further, as shown in FIG. 11(e), the second thin film 402B between eachpattern is removed by normal photolithography or scribing using thepatterning device to form a partition groove 405, and eachcross-sectional element 4 b is separated.

FIG. 13 is a plan view corresponding to FIG. 11(e). The thin film 4 aand the second thin film 402B both having the same thickness which areto be components of the micro-structure 4 are now arranged. In thisembodiment, every cross-sectional element 4 b which is to structure onemicro-structure 4 is arranged regularly in rows and columns.

Next, as in the first embodiment, the substrate 400 on which a pluralityof thin films 4 a are formed is introduced into the vacuum chamber ofthe lamination equipment, and then evacuation of the vacuum chamber,alignment adjustment, removal of contaminated layers, thin film bonding,and transfer are performed.

FIG. 14 shows a laminated layer comprising the first layercross-sectional element 4 b through the twentieth layer cross-sectionalelement 4 b. In this drawing, the shaded portion shows the thin film 4 aconsisting of Al₂O₃ and the non-shaded portion shows the second thinfilm 402B consisting of Al. By repeating the above-mentioned processes,the cross-sectional elements 4 b of the first layer through twentiethlayer are laminated on the stage 302 with interposition of thesacrificial layer 370. When the lamination is completed, the appearanceis seemed to be a rectangular parallelepiped of Al, and the pulley 43,the shaft 41 and two fringes 40 consisting of Al₂O₂ are imbeddedinternally. Finally, the Al rectangular parallelepiped is soaked in anetching solution for dissolving Al to remove only the second thin film402B consisting of Al, and the sacrificial layer 370 is removed, hencethe micro-pulley 43 combined with the shaft 41 consisting of Al₂O₃ iscompleted.

According to the second embodiment, effects described hereinafter areobtained.

(a) As shown in FIG. 10, a micro-structure comprising a plurality ofcomplex combined parts can be manufactured. Because the first thin film4 a of Al₂O₃ and the second thin film 402B of Al having the samethickness are laminated simultaneously, the micro-structure can belaminated correctly even though the micro-structure 4 has an overhangportion (A in FIG. 10(b)) or separate portion (B in FIG. 10(b), furtherthe small gap (G in FIG. 10(b)) between the shaft 41 and pulley 43 ismaintained correctly.

A micro-structure in the form of a micro-gear can be manufactured.

FIG. 15 shows a micro-gear, FIG. 15(a) is an exploded perspective view,and FIG. 15(b) is a longitudinal cross-sectional view. Themicro-structure 4 shown in FIG. 15 is composed of thin films 4 a of thefirst layer through twentieth layer and the micro-structure has astructure that a shaft 41 provided with flanges 40 and 40 on both sidesis inserted into an opening 43 a of the micro-gear 44.

(c) Not only can a micro-structure consisting of a metal or an insulatorbe formed directly but also a micro-structure having a complex structurecomprising a plurality of combined components can be manufactured, andassembling work for manufacturing micro-structures is significantlyreduced.

In this embodiment, the case that combination of ceramics and metalnamely Al₂O₃ for the first thin film and Al for the second thin film isdescribed, however, alternatively, combinations, for example, acombination of a metal and a ceramic such as Al and Al₂O₃, a combinationof a metal and another metal such as Ta and Al, or, Al and Cu, and acombination of two kinds of ceramics such as alumina and siliconnitride, may be used. This combination is determined by considering thebondability to each other and capability of selective etching.

The CMP method is used in this embodiment, however, a method in which athin film is deposited under precise thickness control and the exclusivepattern having the same film thickness is formed by patterning throughtwo photolithography may be used.

The second thin film is removed by etching after all the cross-sectionalelements 4 b are laminated in this embodiment, however, a method inwhich the first thin film is formed of a material which is easy toremove and then the first thin film is removed may be used. A moldcomposed of the second thin film having an inside configurationcomplementary to the target micro-structure is obtained thereby, andthen micro-structures consisting of plastics can be mass-produced byinjection molding, cast molding, or press molding using this mold.

FIG. 16 and FIG. 17 show a thin film deposition substrate in accordancewith the third embodiment. The thin films 4 a of the first layer throughtwentieth layer are formed continuously and separately on the substrate400 in the second embodiment, but in the third embodiment 148 chipshaving a size of 10 mm square are formed on one silicon wafer having asize of 6 inches, and about 7,000 thin films 4 a having the samethickness are arranged two-dimensionally with a 120 μm pitch on eachchip C. In FIG. 16, a pattern shown in FIG. 17(a) is formed onrespective chips C₁, C₂, C,₉, and C₂₀, a pattern shown in FIG. 17(b) isformed on respective chips C₃ and C₁₈, a pattern shown in FIG. 17(c) isformed on respective chips C₄, C₅, C₆, C₁₅, C₁₆, and C₁₇, and a patternshown in FIG. 17(d) is formed on respective chips C₇ through C₁₄.

FIG. 18 shows a laminated layer of chips C composed of the first layerto twentieth layer. The second thin film 402B in the chip C is removedand the sacrificial layer 370 is removed by etching, thereby 7,000micro-structures 4 shown in FIG. 10 are obtained simultaneously, 49,000micro-structures 4 are obtained from one wafer, as the result,micro-structures can be mass-produced. In this embodiment, an embodimentthat one type of micro-structures is arranged in a chip, but a pluralityof different types of micro-structures having different flange diametersand pulley diameters may be arranged.

FIG. 19 shows a patterning equipment 2B in accordance with the fourthembodiment of the present invention. The fourth embodiment has the samestructure as the first embodiment excepting the patterning equipment 2B.The patterning equipment 2B has a vacuum chamber 20, and in the vacuumchamber 20 an ion beam generator 22 and a deflection electrode 23 fordeflecting an ion beam 21 emitted from the ion beam generator 22 basedon slice data of the micro-structure are provided, a thin film 402 isformed on a substrate 400 with interposition of a releasing layer 401 asshown in FIG. 19, then the substrate 400 on which the thin film 402 isformed is introduced into the vacuum chamber 20, and unnecessaryportions or circumference of the thin film 402 is removed by a focusedion beam (FIB) method. In this embodiment, the circumference is removed.“FIB method” generally means a method that vapor of gallium (Ga) isaccelerated by an electric field and focused to a thin beam, and thebeam is scanned by applying a voltage to a deflection electrode andapplied onto desired portions on the target, such a method is generallyused for analysis or observation of a sample or used for fine working asin this embodiment.

Next, operations in this embodiment is described with reference to FIG.20.

FIG. 20 shows a micro-structure 4 to be manufactured in the fourthembodiment. The micro-structure 4 has a drum configuration composed ofthin films first layer to n-th layer. As in the first embodiment, areleasing layer 401 is formed on a substrate 400, and an Al thin film402 having a thickness of 0.5 μm is deposited. Next, as shown in FIG.19, the substrate 400 is introduced into the vacuum chamber 20, and theAl thin film 402 is selectively removed by the FIB method. Though notonly the Al layer is removed but also the substrate surface is slightlyremoved because the etching in the depth direction is controlled not soprecisely in the removal process by the FIB method, the slight removalof the substrate 400 causes no problem because of no micro-parts in thelower layer.

FIG. 21 is a plan view for showing the structure after patterning. Inthe drawing, 405 is a partition groove formed by the FIB method. Theform of patterning is that regions S₁, S₂, S₃, S₄, . . . havingrespective forms corresponding to each cross-sectional form of themicro-structure 4 are arranged with a space between them in therespective cross-sectional elements 4 b. A cross-sectional element 4 bhas an arbitrary form with a size larger than the maximumcross-sectional area of the micro-structure 4 to be manufactured, and isrectangular in this embodiment. Cross-sectional elements 4 b each ofwhich has a cross-sectional pattern of the micro-structure to bemanufactured are arranged two-dimensionally on the entire surface of thesubstrate 400.

Following the process described herein above, the substrate on which aplurality of cross-sectional elements 4 b are formed is introduced intothe vacuum chamber 300 of the lamination equipment 3, and by repeatingprocesses of bonding and transfer the micro-structure 4 composed of theplurality of laminated cross-sectional elements 4 b is completed.

FIG. 22 shows laminated cross-sectional elements 4 b of the first layerthough the n-th layer. The micro-structure 4 composed of central regionsS₁, S₂, S₃, S₄, . . . of the respective cross-sectional elements 4 b isobtained by etching-removing the sacrificial layer 370.

According to the above-mentioned fourth embodiment, because FIB thinfilm patterning allows the process to be performed without a photo-maskfor patterning the thin films, the time required for manufacturing isshortened. The pressure can be kept constant when laminating thin filmsbecause the areas of all the cross-sectional elements 4 b aresubstantially the same. Only the grid region for separating eachcross-sectional element 4 b and the border region in eachcross-sectional element 4 b are removed, and therefore the time requiredfor processing is saved. The drawing precision of about 0.1 μm isobtained, precise forming of a micro-structure is realized.

FIB is used in the above-mentioned embodiment, however, alternatively,an electron beam may be used.

FIG. 23 shows a manufacturing system of micro-structures in accordancewith the fifth embodiment of the present invention. The manufacturingsystem 1 is provided with a film deposition equipment 2A for depositinga thin film on a substrate, an ion implantation device 2C for implantingions onto a region corresponding to each cross-sectional form of atarget micro-structure out of thin films formed by the film depositionequipment 2A, and a lamination equipment 3 for laminating onto aplurality of regions where ions are implanted by surface activatedbonding with irradiation of FAB in the vacuum chamber.

Next, operations in the manufacturing system 1 in accordance with thefifth embodiment are described with reference to FIG. 24 and FIG. 25.

FIG. 24(a) through FIG. 24(d) and FIG. 25(a) through FIG. 25(d) aredrawings to show the manufacturing processes in accordance with thefifth embodiment.

As shown in FIG. 24(a), a releasing layer 401 of an SiO₂ film is formedon the surface of the substrate of a silicon wafer using the filmdeposition equipment 2A, and a non-doped polycrystalline Si (poly-Si)thin film 410 is formed thereon by low pressure chemical vapordeposition (LPCVD). Because the final micro-structure is formed from thepoly-Si thin film 410, sufficient attention should be paid to the filmthickness and film thickness distribution. In this embodiment, thepoly-Si thin film 410 with a thickness of 1.0±0.02 μm is formed. An SOIwafer (Silicon On Insulator) may be used instead of the SiO₂ film andpoly-Si thin film 410 formed on the substrate 400. Next, a siliconnitride film 411 with a thickness of 0.5 μm is formed on the surface ofthe poly-Si thin film 410 by LPCVD, and a window 411 a corresponding tothe cross-sectional form of the micro-structure is provided by theconventional photolithography.

Next, as shown in FIG. 24(b), the substrate 40 is introduced into theion implantation equipment 2 c, boron (B) is implanted up to a highconcentration, for example, of 3×10E19[cm⁻³] or higher. After animplanted mask is removed, annealing is performed in a nitrogenatmosphere to change the ion implanted region to a high concentration p⁺Si region 410 a namely impurity diffused region, which is served as alatent image.

As the result, as shown in FIG. 24(c), the substrate 400 having astructural portion of the micro-structure comprising p⁺ Si region 410 aand a peripheral portion comprising non-doped Si region 410 iscompleted.

Substrates 400 shown in FIG. 24(c) required to form the micro-structureare prepared by applying the above-mentioned process to thin filmscorresponding to other cross-sectional forms of the micro-structure.

Next, as shown in FIG. 24(d), the substrate 400 on which p⁺ Si region410 a corresponding to the cross-sectional form of the first layer andthe substrate 400 on which p⁺ Si region 410 a corresponding to thecross-sectional form of the second layer are bonded together. In detail,two substrates 400 and 400 are introduced into the vacuum chamber of thelamination equipment 3, the surface is cleaned by FAB irradiation as inthe first embodiment, the position of the two substrates 400 and 400 isadjusted, both substrates are bonded together with a pressure, and thesubstrates 400 and 400 are bonded by surface activated bonding.Alternatively, the conventionally well known wafer bonding may also beapplied instead of surface activated bonding. In the “wafer bonding”process, two Si wafers are cleaned sufficiently to make the surfacehydrophilic and superimposed, and heat-treated at about 1,000° C. tobond strongly. In this method, because impurity distribution of theregion formed by ion implantation is changed due to re-diffusion as theresult of the high temperature heat treatment, and the impuritydistribution change causes change of the form of the micro-structure, itis necessary that the size of the implantation mask pattern is correctedpreviously for the change. Surface activated bonding by FAB is thereforepreferable because such correction is unnecessary.

Next, as shown in FIG. 25(a), the back side of the substrate 400 havingthe surface on which the p⁺ Si region 410 a corresponding to thecross-sectional form of the second layer is formed is polished until thereleasing layer 401 of SiO₂ is exposed. Because the releasing layer 401can be detected when it is exposed, it is avoided that the Si thin film410 of the bonding interface is undesirably polished excessively in thepolishing process.

Next, as shown in FIG. 25(b), the releasing layer 401 is removed byetching with buffered hydrofluoric acid, and a semi-finished producthaving two laminated Si thin films 410 is completed.

Subsequently, the above-mentioned processes 25(a) through 25(c) arerepeated to form a semi-finished product having as many laminated Sithin films 410 as required.

Next, as shown in FIG. 25(d), the Si thin film 410 around the p⁺ Siregion 410 a is removed by etching with a KOH solution or EDP(ethylenediamine pyrocatechol) solution in the development process. Thesignificant difference of the etching rate between non-doped Si anddoped Si to these solutions allows the non-doped Si to be removedselectively. Though not shown in the drawing, the back side of thesubstrate 400 may be protected with a silicon nitride film, for example.Finally the releasing layer 401 on the substrate 400 is removed byetching with a buffered hydrofluoric acid, then the completedmicro-structure 4 is separated from the substrate 400.

According to the fifth embodiment, there are the doped micro-structurestructural portion and the non-doped portion surrounding the dopedportion both having the same thickness, the surrounding portionfunctions as a support, an assembled part which has a complex form withan overhang can be therefore formed. The ion-implanted region is formedas a latent image, and the latent image is developed with an EDPsolution after lamination, alternatively the latent image forming methodand development method other than the above-mentioned methods such asselective exposure of photo-resist and development treatment using adeveloping solution may be used.

In this embodiment, a silicon nitride film 411 is used as the implantingmask during the ion implanting process, alternatively a silicon oxidefilm or photo-resist may be used.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the releasing layer to be formed on a substrate surfaceare described hereinafter.

Embodiment 1

Because, by using fluoro polymer (CYTOP, product of Asahi Glass Company)as the releasing layer, a thin layer can be formed on a substrate byspin-coat method, and surface energy is very small (generally very waterrepellent), the adhesion of the film formed on the surface is very low(about 1 MPa), and the film is suitable as the releasing layer. Afterspin-coating of a coupling agent (to improve the adhesion on asubstrate) on an Si wafer or glass substrate, a film with thickness ofabout 2 μm of fluoro polymer (CYTOP) is spin-coated and baked at themaximum temperature of 300° C. to form a releasing layer.

Embodiment 2

By using fluorinated polyimide (OPI-N1005, product of Hitachi ChemicalCo., Ltd.) as the releasing layer a releasing layer can be formed byspin-coat method, and polyimide has a glass transition temperaturehigher than fluoro polymer (CYTOP), and the maximum temperature of filmdeposition and patterning process is higher. After coating of a couplingagent, a film with a thickness of about 5 μm of fluorinated polyimide(OPI-N1005) is spin-coated on a substrate, and baked at the maximumtemperature of 350° C. to form a releasing layer.

Embodiment 3

It is confirmed that a fluorinated surface layer obtained by exposingthe substrate surface to a gas containing fluorine atom exhibits thesame effect. Specifically, an Si wafer, an Si wafer on which oxide filmis formed, or a glass substrate or these substrates coated withnon-fluorinated polyimide introduced into a vacuum equipment (dryetching machine), and plasma treatment is applied using CF₄ gas (gasflow rate of 100 sccm, discharging power of 500 W, pressure of 10 Pa,and time of 10 minutes), this process results in reduced adhesionstrength with the thin film. The same process is also effective usingSF₆ gas.

As described hereinabove, according to the present invention, becausethin films are used as starting material, and a plurality of thin filmsare laminated by bonding, thus the dimensional precision is high andhigh resolution in the lamination direction is realized.

Because a micro-structure composed of thin films consisting of a metalor an insulator can be formed, it is possible to manufacturemicro-structures directly from a metal or an insulator such as ceramics.

By applying a process in which the first thin film and second thin filmare formed with the same film thickness, a plurality of thin films arelaminated, and then the first thin film or second thin film is removedselectively, a micro-structure having a plurality of structural elementsis formed simultaneously, and thus the steps of the manufacturing andassembling work of micro-structures are significantly reduced.

1. A method of forming a micro-structure with a plurality of laminatedthin films, comprising: cleaning one surface of one laminated thin filmof the plurality of laminated thin films and another surface of anotherlaminated thin film of the plurality of laminated thin films that isopposite the one surface in order to remove impurities on the onesurface and the another surface; contacting directly and bondingtogether the one surface and the another surface after cleaning the onesurface and the another surface; and repeating the cleaning of surfacesand the direct contacting and bonding together of surfaces until all ofthe plurality of laminated thin films are bonded together.
 2. The methodaccording to claim 1, wherein the plurality of laminated thin films areplaced in an evacuated vacuum chamber before being cleaned.
 3. Themethod according to claim 1, wherein the surfaces are cleaned byirradiating an inert gas atomic beam onto the surfaces for fast atombombardment treatment.
 4. The method of claim 1, wherein themicro-structure comprises a plurality of combined structural elementswith at least two structural elements which are separated and which aremovable relative to one another.
 5. The method of claim 1, wherein themicro-structure is a mold.
 6. The method of claim 5, wherein the moldhas an inside configuration that matches a target micro-structure formedin the mold by a molding process.
 7. The method of claim 1, wherein theplurality of laminated thin films have a two-dimensionally patternedform.
 8. The method of claim 1, wherein the plurality of laminated thinfilms have a two-dimensionally patterned form, and the thin filmsinclude at least one material selected from the group consisting ofmetals, ceramics and semiconductors.
 9. The method of claim 8, whereinthe thin films comprise at least one material selected from the groupconsisting of aluminum, tantalum, copper, indium, alumina, aluminumnitride, silicon carbide, silicon nitride and silicon.
 10. The method ofclaim 1, wherein the plurality of laminated thin films have atwo-dimensionally patterned form, and the thin films include acombination of thin films having different compositions from each other.11. The method of claim 10, wherein at least one thin film of thecombination of thin films comprises a combination of two differentmaterials selected from the group consisting of metals and ceramics. 12.The method of claim 11, wherein two thin films of the combination ofthin films each comprise a combination of two different materialsselected from the group consisting of metals and ceramics.
 13. Themethod of claim 11, wherein the at least one thin film of thecombination of thin films comprises a metal and a ceramic material. 14.The method of claim 11, wherein the at least one thin film of thecombination of thin films comprises two different metals.
 15. The methodof claim 11, wherein the at least one thin film of the combination ofthin films comprises two different ceramic materials.
 16. The method ofclaim 1, wherein the plurality of laminated thin films is a plurality oflaminated non-adhesive thin films having a two-dimensionally patternedform.
 17. The method of claim 1, wherein the one surface and the anothersurface are activated before bonding.
 18. The method of claim 1, whereinthe one surface and the another surface are directly contacted andbonded together without an oxide film on the one surface and the anothersurface.
 19. The method of claim 1, wherein the one surface and theanother surface are directly contacted and bonded together by surfaceactivated bonding to achieve high dimensional precision in a laminationdirection.
 20. The method of claim 1, wherein the one surface and theanother surface are directly contacted and bonded together during abonding process performed in a vacuum to achieve high dimensionalprecision in a lamination direction.
 21. The method of claim 1, whereinthe one surface and the another surface consists of a materialconsisting of the thin film and exposed at the one surface and theanother surface.